The share of electricity generated by Britain's nuclear power stations has fallen to 15 per cent of total demand - its lowest level in 21 years - government figures indicate.

The decline from a peak of about 30 per cent in 1996 has resulted from a string of technical problems with British Energy's ageing reactors and the scheduled closure of plants.

At only 52 terrawatt hours of a total 378.5 terrawatt hours supplied last year, the figure was the lowest since 1987.

The Nuclear Industry Association gave warning yesterday that nuclear energy's share could slide farther, to less than 10 per cent by 2011, because of further planned reactor closures at Oldbury, Gloucestershire, this year and at Wylfa, Anglesey, in 2010.

Two more plants, at Heysham, Lancashire, and Hartlepool, are scheduled to close in 2014 and two more in 2016. A spokesman for the association said: “We believe this makes it even more important to move forward towards new nuclear development in the UK in a timely fashion to help to deliver a stable-priced, low-carbon economy for the future wellbeing of the country.”

The steep decline in UK electricity produced from nuclear power has emerged as concern mounts over the safety record of the two French state energy giants bidding to regenerate Britain's nuclear industry after the fourth incident of radioactivity of the summer.

Although authorities in France said that the environmental impact of the leaks was limited, they have sapped confidence just as Paris is pushing to export its nuclear technology.

The latest lapse happened at a nuclear waste plant run by a subsidiary of Areva, the group leading a consortium that is in line to take over the management of Sellafield.

Areva, which wants to design the next generation of British nuclear reactors, faced calls to shut down the Tricastin plant in southern France after it was found to have emitted its annual quota of radioactive gas in only six months.

The French Nuclear Safety Authority ordered the company to cease activities resulting in carbon-14 releases until January after the failing, which involved the treatment of radioactive medical waste.

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